After adjusting for bias in meta-analysis seasonal influenza vaccine remains effective in community-dwelling elderly

Maryam Darvishian, Giedre Gefenaite, Rebecca M Turner, Petros Pechlivanoglou, Wim Van der Hoek, Edwin R Van den Heuvel, Eelko Hak*

*Corresponding author for this work

Research output: Contribution to journalReview articleAcademicpeer-review

31 Citations (Scopus)


OBJECTIVE: To compare the performance of the bias-adjusted meta-analysis to the conventional meta-analysis assessing seasonal influenza vaccine effectiveness among community-dwelling elderly aged 60 years and older.

STUDY DESIGN AND SETTING: Systematic literature search revealed 14 cohort studies that met inclusion and exclusion criteria. Laboratory-confirmed influenza, influenza-like illness, hospitalization from influenza and/or pneumonia, and all-cause mortality were study outcomes. Potential biases were identified using bias checklists. The magnitude and uncertainty of biases were assessed by expert opinion. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using random effects model.

RESULTS: After incorporating biases, overall effect estimates regressed slightly toward no effect, with the largest relative difference between conventional and bias-adjusted ORs for laboratory-confirmed influenza (OR, 0.18; 95% CI: 0.01, 3.00 vs. OR, 0.23; 95% CI: 0.03, 2.04). In most of the studies, CIs widened reflecting uncertainties about the biases. The between-study heterogeneity reduced considerably with the largest reduction for all-cause mortality (I(2) = 4%, P = 0.39 vs. I(2) = 91%, P < 0.01).

CONCLUSION: This case study showed that after addressing potential biases influenza vaccine was still estimated effective in preventing hospitalization from influenza and/or pneumonia and all-cause mortality. Increasing the number of assessors and incorporating empirical evidence might improve the new bias-adjustment method.

Original languageEnglish
Pages (from-to)734-744
Number of pages11
JournalJournal of Clinical Epidemiology
Issue number7
Publication statusPublished - Jul-2014


  • Meta-analysis
  • Bias adjustment
  • Observational studies
  • Seasonal influenza
  • Vaccination
  • Community-dwelling elderly

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